The present invention relates to a vehicle body transfer machine and a method thereof for use in a vehicle body assembly line of an automobile and more particularly, to a vehicle body transfer machine of a general-purpose type and a method thereof specifically suited for transferring vehicle bodies of plural vehicle""s models in a so-called mixed flow manufacturing system.
Japanese Patent Publication No. 2745841 discloses a vehicle body transfer machine of a general-purpose type.
Such a vehicle body transfer machine is generally constructed of a vehicle body assembly line which includes a plurality of work stages located in a spaced relationship with a given interval, with a final stage and an initial stage being connected to one another with a return line to form a circulated line to enable a transfer truck, which supports the vehicle body, to be circulated in use. In such a structure, the transfer truck is constructed of a plurality of multi-axis units each with an operating freedom in orthogonal three axes, with each multi-axis unit carrying at its distal end a locating pin whose three-dimensional position can be substantially changed over to an arbitrary selected position. The circulated line is constructed of a change-over stage mounted with a change-over robot. With such a structure, when transferring the vehicle bodies of another vehicle""s model using the transfer truck, the change-over unit operates to release the coupling force (restricting force) of brake units adapted to restrict the operating freedoms of respective multi-axis units and subsequently to allow the change-over robot in the change-over stage to shift the locating pin of each multi-axis unit to an arbitrary position to be positioned while retaining the locating pin. Then, the operating freedom of each multi-axis unit is restricted again, completing the change-over operation of the work position of each locating pin.
More specifically, in such a structure of the vehicle transfer machine, each multi-axis unit includes air cylinders contained therein for restoring original positions of respective operating freedoms in the orthogonal three axes. With such an arrangement, when releasing the coupling force (the restricting force) of each brake unit by supplying compressed air thereto from outside during the change-over operation of the locating pin, simultaneously, the three air cylinders are operated to cause the locating pin to move to original positions correlated with respective directions to be restored at the original point at once. Thus, it is required for the vehicle body transfer machine to undesirably employ the air cylinders specific for respective operating freedoms to restore the original point. This results in an increase in the number of component parts, with a resultant complicated structure and large size in structure.
Further, when changing over the position of the locating pin, since an annular recessed portion formed near the locating pin is gripped with the robot""s hand and is moved in the respective positions at a stretch using the operating freedom in the orthogonal three axes in the X-, Y- and Z-directions, there is a difference in distance between the annular recessed portion, which the force of the robot is applied, and a relevant slide portion for each operating freedom. This causes a difference in momentum due to resistance of the slide portion such that the robot""s hand encounters a difficulty in a smooth movement in either direction of the operating freedom with a resultant extremely degraded positioning precision in such a direction of the operating freedom.
Also, the hand of the change-over robot has no function to correct a relative positioning error caused during gripping operation of the hand and no function to detect that the annular recessed portion has been gripped. Consequently, even with the presence of displacement in position for some reasons such that the hand is unable to grip the annular recessed portion by any possibility, the change-over robot tends to carry out the regular operation, with a degraded reliability in operation of the vehicle body transfer machine.
The present invention has been made with the above view and has an object to provide a vehicle body transfer machine and a method thereof which is able to change over a three-dimensional position of a locating pin in a smooth and reliable manner without the need for actuators such as air cylinders correlated in three axes of an operating freedom of the locating pin.
According to one aspect of the present invention, there is provided a vehicle body transfer machine transferring a vehicle body along a transfer path by using a transfer truck with which the vehicle body is supported, the transfer truck being returned to an initial starting position of the transfer path for a repeated use when transfer of the vehicle body is terminated. The vehicle body transfer machine is provided with: a jig change-over stage located before the initial starting position of the transfer path; a plurality of locator jigs respectively mounted on the transfer truck in spaced relationship to each other, each of the plurality of locator jigs including an upwardly directed locating pin to position the vehicle body and having operating freedoms in orthogonal three axes involving horizontal two directions of X- and Y-directions and a vertical direction of a Z-direction to respectively alter a three-dimensional position of the locating pin, and a plurality of lock units being attached to each of the plurality of locator jigs to restrict the operating freedoms thereof so as to lock the locating pin at the three-dimensional position; an unlock-operating unit connected to the jig change-over stage to unlock-operate the plurality of lock units when the transfer truck is positioned in the jig change-over stage; and a jig change-over unit mounted on the jig change-over stage, the jig change-over unit being associated with corresponding one of the plurality of locator jigs to allow the operating freedoms thereof to be utilized for changing over the three-dimensional position of the locating pin of the corresponding one of the plurality of locator jigs to an arbitral three-dimensional position, while the unlock-operating unit being actuated to unlock-operate the plurality of lock units of the corresponding one of the plurality of locator jigs. The jig change-over unit includes a socket portion engageable with the locating pin of the corresponding one of the plurality of locator jigs, the socket portion being moveable toward the locating pin to be brought into engagement therewith under a first unlock condition established when the unlock-operating unit unlock-operates the plurality of lock units, which is correlated with the horizontal two directions, of the corresponding one of the plurality of locator jigs to perform a relative positioning in the two horizontal directions between the jig change-over unit and the corresponding one of the plurality of locator jigs.
In other words, there is provided a vehicle body transfer machine transferring a vehicle body along a transfer path by using a transfer truck with which the vehicle body is supported, the transfer truck being returned to an initial starting position of the transfer path for a repeated use when transfer of the vehicle body is terminated. The vehicle body transfer machine is provided with: a jig change-over stage located before the initial starting position of the transfer path; a plurality of locator jigs respectively mounted on the transfer truck in spaced relationship to each other, each of the plurality of locator jigs including an upwardly directed locating pin to position the vehicle body and having operating freedoms in orthogonal three axes involving horizontal two directions of X- and Y-directions and a vertical direction of a Z-direction to respectively alter a three-dimensional position of the locating pin, and a plurality of lock units being attached to each of the plurality of locator jigs to restrict the operating freedoms thereof so as to lock the locating pin at the three-dimensional position; unlock-operating means for unlock-operating the plurality of lock units when the transfer truck is positioned in the jig change-over stage; and jig change-over means for changing over the three-dimensional position of the locating pin of corresponding one of the plurality of locator jigs to an arbitral three-dimensional position, while the unlock-operating means being actuated to unlock-operate the plurality of lock units of the corresponding one of the plurality of locator jigs. The jig change-over means includes socket means for engaging with the locating pin of the corresponding one of the plurality of locator jigs, the socket means being moveable toward the locating pin to be brought into engagement therewith under a unlock condition established when the unlock-operating means unlock-operates the plurality of lock units, which is correlated with the horizontal two directions, of the corresponding one of the plurality of locator jigs to perform a relative positioning in the two horizontal directions between the jig change-over means and the corresponding one of the plurality of locator jigs.
Besides, there is provided a method transferring a vehicle body along a transfer path by using a transfer truck with which the vehicle body is supported, the transfer truck being returned to an initial starting position of the transfer path for a repeated use when transfer of the vehicle body is terminated. The method provides a jig change-over stage located before the initial starting position of the transfer path; provides a plurality of locator jigs respectively mounted on the transfer truck in spaced relationship to each other, each of the plurality of locator jigs including an upwardly directed locating pin to position the vehicle body and having operating freedoms in orthogonal three axes involving horizontal two directions of X- and Y-directions and a vertical direction of a Z-direction to respectively alter a three-dimensional position of the locating pin, and a plurality of lock units being attached to each of the plurality of locator jigs to restrict the operating freedoms thereof so as to lock the locating pin at the three-dimensional position; provides a jig change-over unit mounted on the jig change-over stage, the jig change-over unit being associated with corresponding one of the plurality of locator jigs to allow the operating freedoms thereof to be utilized for changing over the three-dimensional position of the locating pin of the corresponding one of the plurality of locator jigs; positions the transfer truck in the jig change-over stage; unlock-operates the plurality of lock units of each of the plurality of locator jigs when the transfer truck is positioned in the jig change-over stage; and changes over the three-dimensional position of the locating pin of each of the plurality of locator jigs to an arbitral three-dimensional position by using the jig change-over unit, while unlock-operating the plurality of lock units of each of the plurality of locator jigs. The jig change-over unit is moved toward the locating pin of the corresponding one of the plurality of locator jigs to be brought into engagement therewith under a unlock condition, which is established by unlock-operating the plurality of lock units, which is correlated with the horizontal two directions, of the corresponding one of the plurality of locator jigs to perform a relative positioning in the two horizontal directions between the of jig change-over unit and the corresponding one of the plurality of locator jigs.
Other and further features, advantages, and benefits of the present invention will become more apparent from the following description taken in conjunction with the following drawings.